This invention relates to controlled force actuating systems and more particularly, to an actuating system in which an actuating force is supplied by controlled release of a loaded spring. The actuating system is particularly applicable to the development of normal forces for friction devices such as power transmitting clutches but is also useful in other applications.
Automotive power transmitting or starting clutches represent one of the more challenging applications of controlled force actuating systems in which a relatively large amount of energy stored in a spring must be controlled during release and restored to the spring. Such clutches employ frictionally engaged torque transmitting components which operate at a torque capacity essentially proportional to an axial clamping force applied by an actuating spring. The force of the actuating spring is modulated such that transmitted torque may be controlled reversibly between minimum and maximum values. Traditionally, the relatively large force actuating springs of automotive clutches have been operated by control systems involving levers, ball ramps or other force reduction devices by which the actuating spring may be controlled by a foot pedal, an electric motor, or hydraulic actuators, for example.
The conventional control systems for automotive starting clutches are not only complex and space consuming, but also, they are not suited to automation because of the large amounts of energy required for their operation. In this latter respect, the development of on-board computers in automotive vehicles has given rise to much interest in automating the operating of starting clutches and the power transmissions with which they are used. In spite of many recent attempts to accomplish such automation, the energy requirements to retract and control the release of the clutch spring have been a major obstacle.
Hence, there is an acute need for a controlled force actuating system by which a large spring force can be exerted but which can be operated by a relatively small amount of control energy. This need exists not only in automatic clutch applications, but also in numerous other applications where a force must be applied between action and reaction members, under control through a range of from minimum to maximum force values, as in rotatable or linear friction brakes, clutch packs for automatic transmissions, autoclaves, all given as limited examples only.